The invention relates to compositions and methods for use in treating bone disease associated with myeloma. More specifically, the invention concerns the use of inhibitors of proteasomal and NF-xcexaB activity for this purpose.
Multiple myeloma is the second most common hematologic malignancy producing some 15,000 new diagnosed cases each year in the United States with the number of existing myeloma patients numbering between 30,000 to 40,000 (Mundy et al. Seminar Oncol (1986) 3:291). Eighty percent of whom suffer from devastating osteolytic bone destruction caused by increases in osteoclast formation and activity (Mundy et al. (1986), supra). The associated bone destruction can cause severe bone pain, pathologic fractures, spinal cord compression, and life-threatening hypercalcemia. It has been reported that multiple myeloma cannot be cured by standard chemotherapy or stem cell transplantation (Attai et al. Blood (1996) 87(4):1495-1501).
Myeloma bone disease results in severe morbidity and potential mortality. Accordingly, the development of strategies and treatments that control the osteolytic bone destruction resulting in these patients has become of vital importance.
However, the pathologic mechanisms responsible for increased osteoclast activity in multiple myeloma patients are unknown. Further, the accompanying bone lesions that occur in the patients take on several pattern forms. Occasionally, patients develop discrete osteolytic lesions in association with solitary plasmacytomas. Other patients have diffuse osteopenia, which mimics the appearance of osteoporosis, and results from the diffuse dispersion of the myeloma cells throughout the axial skeleton. In most atients, there are multiple discrete lytic lesions occurring adjacent to nests of myeloma ells. Hypercalcemia occurs as a consequence of bone destruction in about one third of atients with advanced bone disease. Rarely do patients with myeloma fail to develop lytic lesions or bone loss, instead they have an increased new bone formation around myeloma cells. This rare situation is known as osteosclerotic myeloma.
Osteolytic bone lesions are the most common deleterious skeletal manifestation in patients with myeloma. Although the precise molecular mechanisms remain unclear, nevertheless observations over 15 years have revealed several facts. First, the mechanism by which bone is destroyed in myeloma occurs via the osteoclast, the normal bone-resorbing cell. Second, osteoclasts accumulate on bone-resorbing surfaces in myeloma adjacent to collections of myeloma cells. Thus, it appears that the mechanism by which osteoclasts are stimulated in myeloma is a local one. Third, it has been known for many years that cultures of human myeloma cells, in vitro, produce several osteoclast-activating factors, including lymphotoxin, interleukin-1 (IL-1), and interleukin-6 (IL-6). Fourth, hypercalcemia occurs in approximately one third of patients with myeloma at some point during the course of the disease. Hypercalcemia is always associated with markedly increased bone resorption, and frequently with the impairment in glomerular filtration. Fifth, the increase in osteoclastic bone resorption in myeloma is usually associated with a marked impairment in osteoblast function. Alkaline phosphatase activity in the serum is decreased or remains in the normal range, in contrast to patients with other types of osteolytic bone disease. Also, radionuclide scans do not show evidence of increased uptake, which indicates impaired osteoblast response to the increase in bone resorption.
Various mediators have been implicated in the stimulation of osteoclast activity in patients with multiple myeloma, including lymphotoxin (tumor necrosis factor-xcex2 (TNFxcex2)), interleukin-1-beta (IL-1xcex2), parathyroid hormone-related protein (PTHrP), and interleukin-6 (IL-6). However, reports of factors that are produced by myeloma cells have been wholly inconsistent. Some studies have been inconclusive due to the presence of other contaminating cell types including stromal cells and macrophages in the multiple myeloma cell population. IL-6 is a major myeloma growth factor that enhances the growth of several myeloma cell lines and those cells freshly isolated from myeloma patients (Bataille et al. J Clin Invest (1989) 84:2008). IL-6 production can be detected in about 40% of freshly isolated myeloma cells by PCR, but only 1 in 150 patients studied show detectable IL-6 production by immunocytochemistry or ELISA assays (Epstein J. Hematology/Oncology Clinics of North America (1992) 6:249-256. The IL-6 receptors were only detected in 6 of 13 samples from patients with multiple myeloma (Bataille et al. Hematology/Oncology Clinics of North America (1992) 6:285-295). Furthermore, mature myeloma cells have been reported to have a minimal proliferative response to interleukin-6. Interleukin-11 (IL-11) has an IL-6-like activity on plasmacytomas, but to date no one has demonstrated that myeloma cells produce IL-11. Bataille and coworkers (Bataille et al. Blood (1995) 86(2):685-91) have shown that the perfusion of 5 patients with refractory myeloma with an antibody of IL-6 decreased the size of the myeloma cell burden in only 2 of these patients.
In addition to IL-6 and IL-1xcex2, TNFxcex1 and lymphotoxin have been implicated as mediators of bone destruction in multiple myeloma. IL-6 is an extremely potent bone-resorbing agent that induces hypercalcemia in animal models in the absence of renal failure (Boyce et al. Endocrinology (1989) 125:2780-2783). In contrast, hypercalcemia rarely occurs in myeloma patients without renal failure. More importantly, in highly purified myeloma cells, no IL-1xcex2 and only rare TNFxcex1 production can be detected, suggesting that other contaminating cell types such as macrophages may be the source of the IL-1xcex2 and TNFxcex1 (Epstein (1992), supra). Similarly, lymphotoxin is produced by most human myeloma cell lines (Bataille et al. (1995), supra) but does not appear to be produced by myeloma cells in vivo (Alsina et al. Blood (1996) 87(4):1495-1501). In addition to IL-1xcex2, TNFxcex1, lymphotoxin and IL-6, myeloma cells produce a truncated form of M-CSF which is biologically active. However, M-CSF does not cause hypercalcemia or induce osteoclast formation by itself in human marrow cultures (MacDonald et al. J Bone Miner Res (1986) 1:227-233). Thus, the specific role played by many of these factors in osteolytic bone disease occurring in myeloma patients has not been definitively illustrated in vivo. Thus, the known cytokines do not entirely account for the bone resorption observed in these patients.
Furthermore, freshly isolated marrow supernatants from the affected bones in myeloma patients contain a bone-resorbing activity that comprises an unknown resorbing cytokine. These data suggest that myeloma cells produce factors in the marrow microenvironment that differ from those produced by the cells in vitro and that this factor(s) is not a cytokine previously known to be produced by myeloma cells.
NF-xcexaB is a transcription factor which regulates the expression of the kappa light chain gene in murine B lymphocytes, but is now known to be expressed ubiquitously. A number of different NF-xcexaB proteins have been identified and well-characterized (Siebenlist et al. Annu Rev Cell Biol (1994) 10:405-455; see also, Baeurele et al. Cell (1996) 87:13-20). NF-xcexaB in its active state is a heterodimer, which consists usually of two subunits. The most common subunits are known as P65 and P50; another common subunit is P52. Different combinations of these subunits may be involved in the observation of different target genes. In unstimulated cells, NF-xcexaB is both present in the cytoplasm and bound to other proteins known as IkBxcex1 and IkBxcex2 and prevent it from entering the nucleus. Upon stimulation of cells, specific enzymes lead to the phosphorylation of IkB, which in turn leads to its rapid degradation in the proteasomes. Upon degradation of IkB, NF-xcexaB is then available to translocate to the nucleus. In the nucleus, NF-xcexaB binds to promoter sequences of target genes and leads to their transcription. Proteasome activity is thus required for NF-xcexaB translocation.
The proteasome is a non-compartmentalized collection of unrelated proteases which form a common architecture in which proteolytic subunits are self-assembled to form barrel-shaped complexes (Baumeister et al. Cell (1998) 92:367-380). The proteasome contains an array of distinct proteolytic activities inside eukaryotic cells; among these are activities that assist in translocating NF-xcexaB to the nucleus where it exerts its effect. Compounds which inhibit proteasomal activity reduce NF-xcexaB activity by limiting its capacity to be translocated to the nucleus (Barnes et al. New Engl J Med (1997) 336:1066-1071).
It has recently been shown that mice lacking expression of the transcription factor NF-xcexaB develop abnormal bone conditions, such as osteopetrosisxe2x80x94the converse of osteoporosisxe2x80x94due to an absence of osteoclast formation (Franzoso et al. Genes and Dev (1997) 11:3482-3496). Osteopetrosis is characterized by absence of osteoclast function, along with the filling in of the marrow cavity with osteocartilagenous material. However, the mechanisms of osteoclast formation in normal mice as compared to such formation in myeloma are different; the cytokine pattern characterizing osteoclast formation in myeloma has not been characterized. As the mechanisms are different, it is unpredictable what the effect of NF-xcexaB gene depletion would be on myeloma bone disease.
Orlowski, R Z, et al, Cancer Res (1998) 58:4342-4348 have shown that lymphoma tumor growth is inhibited by a proteasome inhibitor. However, the etiologies of lymphoma and of myeloma are quite different, and it would not be predictable whether agents effective against one would or would not be effective against the other.
The present invention adds to the repertoire of agents which inhibit myeloma bone disease by providing drugs that will inhibit key proteins and enzymes involved in proteasomal activity and which decrease the activity of the nuclear transcription factor NF-xcexaB, and thus inhibit the bone disease associated with myeloma. In accordance with the present invention, inhibition of the functions of proteasomal proteins and of the transcription factor NF-xcexaB in myeloma cells leads to decreased myeloma bone disease. Thus, assessing a candidate compound for its ability to inhibit proteasomal proteins or NF-xcexaB provides a useful means to identify agents to treat myeloma bone disease.
Thus, in one aspect, the invention provides methods to identify compounds that are useful to treat myeloma bone disease by assessing their capacity to inhibit proteasome activity or to inhibit the activity of the transcription factor NF-xcexaB, or to inhibit production of these moieties. In another aspect the invention provides a method to treat myeloma bone disease by administering to a subject in need of such treatment a compound that inhibits proteasome activity, the activity of transcription factor NF-xcexaB, or the production of the proteasome enzymes or NF-xcexaB.
In accordance with the present invention, there are provided methods of treating bone disease associated with myeloma in subjects suffering therefrom. The method comprises administering to the subject, in a sufficient amount, a compound which inhibits proteasomal activity and function, or the activity of the nuclear transcription factor NF-xcexaB, or the production of these proteins.
As employed herein, the term xe2x80x9csubjectxe2x80x9d embraces human, as well as other animal species, such as, for example, canine, feline, bovine, porcine, rodent, and the like.
As used herein, the terms xe2x80x9ctreatxe2x80x9d or xe2x80x9ctreatmentxe2x80x9d include a postponement of development of bone disease symptoms and/or a reduction in the severity of such symptoms that will, or are expected to develop. Thus, the terms denote that a beneficial result has been conferred on a vertebrate subject with myeloma bone disease.
The compositions of the invention may be administered systemically or locally. For systemic use, the compounds herein are formulated for parenteral (e.g., intravenous, subcutaneous, etc.) delivery according to conventional methods. Intravenous administration can be by a series of injections or by continuous infusion over an extended period of time. Treatment will continue until the desired outcome is achieved. In general, pharmaceutical formulations will include a compound of the present invention in combination with a pharmaceutically acceptable vehicle.
Parenteral preparations comprise particularly sterile or sterilized products. Injectable compositions may be provided containing the active compound and any of the well known injectable carriers. These may contain salts for regulating the osmotic pressure.
Within the present invention, an xe2x80x9ceffective amountxe2x80x9d of a composition is that amount which produces a statistically significant effect. For example, an xe2x80x9ceffective amountxe2x80x9d for therapeutic uses is the amount of the composition comprising an active compound herein required to provide a clinically significant decreases in the viability of human myeloma cells or reduces tumor markers in the sera obtained from the affected subjects. Such effective amounts will be determined using routine optimization techniques and are dependent on the particular condition to be treated, the condition of the patient, the route of administration, the formulation, and the judgment of the practitioner and other factors evident to those skilled in the art. The dosage required for the compounds of the invention is manifested as a statistically significant difference in tumor volume, delay of onset of limb paralysis or tumor marker indicia between treatment and control groups. General guidance for treatment regimens is obtained from experiments carried out in animal models of the disease of interest.
The dosage of the compounds of the invention will vary according to the extent and severity of the need for treatment, the activity of the administered compound, the general health of the subject, and other considerations well known to the skilled artisan.
The compounds useful in the methods and compositions of the invention are inhibitors of proteasomal activity or of the transcription factor NF-xcexaB. Known inhibitors of these activities can be ascertained from the literature and compounds can be tested for these activities using assays known in the art. In addition, inhibitors which lower the level of effective expression of the nucleotide sequence encoding the enzymes that have proteasomal activity or of the nucleotide sequence encoding NF-xcexaB can be assessed and used in the invention methods.
Examples of compounds useful in the invention are as follows:
See, for example, Vinitsky, A. et al. J Biol Chem (1994) 269:29860-29866; Figueiredo-Pereira, M. E. et al. J Neurochem (1994) 63:1578-1581; Wojcik, C. et al. Eur J Cell Biol (1996) 71:311-318.
In the foregoing list, lactacystin is known to be an irreversible inhibitor of proteasome activity. It binds to the xcex2 catalytic subunit and is a specific inhibitor of the 20S proteasome. It also irreversibly inhibits NF-xcexaB.
SN50 is the NLS (nuclear localization sequence) of p50 plus the hydrophobic region of K-FGF. It inhibits the translocation of the NF-xcexaB active complex to the nucleus.
Certain peptidyl epoxy ketones such as EST are irreversible inhibitors of the proteasomes. MG-132 shows activity against the chymotryptic activity of the 20S protein without affecting its ATPase or isopeptidase activity and reversibly inhibits NF-xcexaB activity. MG-115 and MG-341 show similar activities to MG-132. Various other inhibitors of NF-xcexaB are less active in the ABA assay. These include capsaicin, curcumin, and resiniferatoxin. Other compounds known to inhibit NF-xcexaB are gliotoxin and PDTC (1-pyrrolidine carbothiotic acid). Various other compounds such as BAY-11-7082 and BAY-11-7085 as well as calyculin-A inhibit phosphorylation of NF-xcexaB. Calpain inhibitor inhibits calpain 1 and the proteasome; other compounds such as olomoucine and roscovitine inhibit cdk2 and/or cdk5.
Compounds which inhibit the production of the enzymes having proteasomal activity or of NF-xcexaB can be assessed by measuring the level of production of these proteins in the presence and absence of candidate compounds. The levels of production can be readily measured in in vitro systems using, for example, immunoassays for the level of protein produced. The levels of such proteins can also be assessed by utilizing, for example, methionine labeling and size separation of proteins in the cells to be assessed. In order to effect a convenient level of protein production for measurement, it is advantageous to use recombinant expression systems for the relevant enzymes or the NF-xcexaB so that substantial amounts are produced.
Typical approaches to inhibiting the production of NF-xcexaB or proteasome enzymes include the use of antisense technology or the formation of triplexes with double-stranded forms of nucleotide sequences relevant in the expression of the genes. In addition, various small molecules may also inhibit this production.
Radl et al. (Am J Pathol (1988) 132:593-597) described a murine model of myeloma which occurred spontaneously in aging mice of the C57 BL/KaLwRij strain. This condition occurred upon aging in approximately one (1) mouse of this strain for every two-hundred (200), and led to a monoclonal gammopathy with all of the characteristic features of the human disease, including growth of malignant cells in the bone marrow and characteristic skeletal lesions. Id. By transplantation of the fresh or frozen myeloma cells by intravenous injection into recipients of the same strain, the disease can be produced more precisely. More recently, Manning et al. (Br J Cancer (1992) 66:1088-1093) described a cell line derived from one of these myelomas.
To develop a better animal model of human myeloma bone disease, a cell line was established and subcloned from this murine myeloma by Garrett et al. Bone (1997) 20(6):515-20. This cell line (ST33) causes osteolytic bone lesions in mice characteristic of human myeloma bone disease. Osteolytic lesions were determined by animal x-rays and quantified. The cell line produces IL-6, but grows independently of exogenous IL-6. Mice inoculated intravenously with the cultured cells predictably develop an identical disease to the mice injected intravenously with fresh bone marrow-derived myeloma cells, including monoclonal gammopathy and radiologic bone lesions. Some of the mice became hypercalcemic, and the bone lesions are characterized by increased osteoclast activity. Identical results were obtained in inoculated Nu/Bg/XID mice with cultured murine myeloma cells.
This model is used to determine the mechanisms by which the myeloma cells cause osteoclast activation, since mice can be inoculated with a precise numbers of cells and it can accurately be predicted when the mice will develop bone lesions, paraplesia, and become hypercalcemic.
It has been recently shown that transfer of cells derived from other 5T myelomas such as 5TGM-1 into inbred C57BL/KaLwRij strain of mice reliably produce myeloma bone disease with involvement of non-bone organs such as the liver and kidney. The animals have elevated serum levels of IgG2b. 5TGM-1 cells are IL-6 independent. More recently the role of adhesion molecules in the induction of bone-resorbing cytokines by these myeloma cells in vitro was demonstrated.
5TGM-1 myeloma cells were initially derived from a myeloma, designated 5TGM-1, which arose spontaneously in an aged C57BL/KaLwRij mouse, as reported by Dallas et al. (to be published in Blood (1998)). 5TGM-1 cells were propagated from the bone marrow of this mouse, maintained in Iscove""s Modified Dulbecco""s Medium(trademark) (xe2x80x9cIMDMxe2x80x9d, available at Life Tech. Inc, Gaithersburg, Md.), and supplemented with 10% Fetal Bovine Serum(trademark) (xe2x80x9cFBSxe2x80x9d, Summit, Fort Collins, Colo.) and 1% penicillin-streptomycin solution (GIBCO, Grand Island, N.Y.) at 37xc2x0 C. in 5% CO2 atmosphere. Bone marrow transfer of 5TGM-1 myeloma in the inbred C57BL/KaLwRij strain of mice also reliably produced myeloma disease exhibiting all the features of human myeloma, such as severe osteolysis and involvement of non-bone organs such as liver and kidney. Based on the histological examination of affected organs in the STGM-1-bearing mice and the increased serum level of monoclonal IgG2b confirmed by SDS-PAGE(trademark), 5TGM1 was defined as a murine myeloma.
Still another model of myeloma bone disease was developed by injecting the human myeloma cell line ARH77 into sublethally irradiated SCID(trademark) mice (Alsina et al. Blood (1996), supra). These animals developed hypercalcemia, lytic bone lesions and the histologic finding characteristic of human myeloma.